This invention relates to pelletizing or briquetting fine particles of coal or coke. More particularly, the invention relates to a process in which the pelletizing of such particles is improved by a specific combination of steps that make it feasible to use waste dust from grain elevators as a binder comprising finely divided by-product or co-product collected during the transport and storage of one or more types of grains, with substantially no preprocessing of the coal or coke.
Numerous processes have been proposed for pelletizing or briquetting particles of coal or coke, for example, in patents such as the following: U.S. Pat. No. 44,994, issued over a century ago, teaches that coal dust can be pelletized by saturating it with a solution of starch, pressing or otherwise forming it into blocks or lumps and drying it, in the sun or by other suitable means. U.S. Pat. No. 852,025 discloses preparing coal for briquetting by drying and heating it, mixing in an asphaltic binder material, then heating, cooling, and compacting the mixture. U.S. Pat. No. 1,121,325 discloses briquetting coal by mixing dry coal and starch, then adding steam which is saturated with oil, then compressing and thermally drying the mixture. U.S. Pat. No. 1,851,689 discloses briqueting coal by mixing the coal with a starch/oil emulsion then autoclaving it at 300.degree. F. U.S. Pat. No. 4,049,392 discloses an extrusion apparatus described in U.S. Pat. No. 3,989,433, for extruding rod-like bodies from coal-containing particulate mixtures, and having means for adjusting the length and density of the extruded particles.